Members of a new group of chitinase-like genes are expressed preferentially in cotton cells with secondary walls

• Published in: Plant molecular biology Vol. 54; no. 3; pp. 353 - 372
• Main Authors: Zhang, D, Hrmova, M, Wan, C.H, Wu, C, Balzen, J, Cai, W, Wang, J, Densmore, L.D, Fincher, G.B, Zhang, H
• Format: Journal Article
• Language: English
• Published: Netherlands Springer Nature B.V 01.02.2004
• Subjects: Amino Acid Sequence; amino acid sequences; Bacteria; beta-glucuronidase; Blotting, Northern; Catalysis; cell growth; Cell Wall - genetics; Cell Wall - metabolism; cell walls; Cellulose; Chitin; Chitinase; Chitinases - chemistry; Chitinases - genetics; Chitinases - metabolism; complementary DNA; Cotton; DNA, Complementary - chemistry; DNA, Complementary - genetics; DNA, Plant - chemistry; DNA, Plant - genetics; enzyme activity; gene expression; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes; Glucuronidase - genetics; Glucuronidase - metabolism; Gossypium - cytology; Gossypium - genetics; Gossypium hirsutum; messenger RNA; Models, Molecular; Molecular Conformation; Molecular Sequence Data; Multigene Family - genetics; nucleotide sequences; Phylogeny; Plant Proteins - chemistry; Plant Proteins - genetics; Plant Proteins - metabolism; Plants, Genetically Modified; promoter regions; Proteins; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; reporter genes; RNA, Plant - genetics; RNA, Plant - metabolism; Sequence Alignment; Sequence Analysis, DNA; Sequence Homology, Amino Acid; transcription (genetics); transgenic plants
• ISSN: 0167-4412; 1573-5028
• DOI: 10.1023/B:PLAN.0000036369.55253.dd

Two homologous cotton (Gossypium hirsutum L.) genes, GhCTL1 and GhCTL2, encode members of a new group of chitinase-like proteins (called the GhCTL group) that includes other proteins from two cotton species, Arabidopsis, rice, and pea. Members of the GhCTL group are assigned to family GH19 glycoside hydrolases along with numerous authentic chitinases (http://afmb.cnrs-mrs.fr/CAZY/index.html), but the proteins have novel consensus sequences in two regions that are essential for chitinase activity and that were previously thought to be conserved. Maximum parsimony phylogenetic analyses, as well as Neighbor-Joining distance analyses, of numerous chitinases confirmed that the GhCTL group is distinct. A molecular model of GhCTL2 (based on the three-dimensional structure of a barley chitinase) had changes in the catalytic site that are likely to abolish catalytic activity while retaining potential to bind chitin oligosaccharides. RNA blot analysis showed that members of the GhCTL group had preferential expression during secondary wall deposition in cotton lint fiber. Cotton transformed with a fusion of the GhCTL2 promoter to the beta-D-glucuronidase gene showed preferential reporter gene activity in numerous cells during secondary wall deposition. Together with evidence from other researchers that mutants in an Arabidopsis gene within the GhCTL group are cellulose-deficient with phenotypes indicative of altered primary cell walls, these data suggest that members of the GhCTL group of chitinase-like proteins are essential for cellulose synthesis in primary and secondary cell walls. However, the mechanism by which they act is more likely to involve binding of chitin oligosaccharides than catalysis.